BB33
Looking at all of that surface area that needs fiberglassing… I wonder if this boat is a candidate for Kelsall’s KSS building, on a pre-finished table? One can buy 3mm “whiteboard” material—it’s thin micarta bonded onto masonite hardboard—for $13/sheet at the big box stores. Lay this on a base of OSB strandboard, at another $12/sheet and you could have a 4-sheet table, complete with all framing, for less than $200. Now you can lay down resin, cloth, then the plywood, all pre-cut and puzzle-jointed together. Throw plastic over it and use a shop vac to suck it down, and bang; pre-finished and pre-cut hulls, sides, decks, bulkheads.
You’d need to drill 1/8” holes on perhaps 3” centers to get the vacuum through the plywood (that’s a lot of holes!), but these get filled with resin during the layup and never need any finishing.
Chris put an idea into my head that just won’t leave; finish the inside—the entire inside—with peel-ply. This is then ready for secondary bonding where needed (filleted joints), but just left as peeled-away peel-ply everywhere else—non-slip, pre-finished, non-shiny (with some colorant in the resin if you don’t want raw plywood color).
What’s not to like?
Dave
(I wonder what would happen if you built an entire boat out of OSB strandboard??)
I’ve been having the same debate with myself about the table build. It’s big and would use more space than I have to build. The resin infusion would require multiple resin feeds on 24’, and I sure would not risk that much set up time and material on a shop vac. Pinholes and vacuum leaks are hard enough to find, and low budget efforts at resin infusion seem like Mr. Murphy’s laws will meet Occam’s Razor with a vengeance.
My current thoughts are wet layup, peel ply and bagging the outside of the ply like a normal cold molding build - after the hull is on the strongback. I know it’ll be +10 - 20% resin heavy compared to infusion, and twice the build effort (repeating the inside glassing once done the outside, but it pushes the glassing later in the process and allows me to build the hull in sections before it gets glassed. I’ve watched Derek Kelsall’s KSS seminar DVD and gone through his material in depth, but I feel that using plywood instead of foam kind of already downgrades the result.
This kind of hull is already pretty experimental and I would rather spend the money on foam core once it is proven effective. There is no way to know if the resulting boat will be worth $2K+ of corecell, a bigger build facility etc. until you build and sail a plywood cheapie first. I also debate putting lots of money into a hull with no resale value when it is effectively a testbed. I accept the fact that people like us build proas for ourselves as everyone else just can’t get enough brain cells warmed up and functioning to bother understanding the concepts.
I also see this as building two hulls - once immersed in water and the other bigger one flipped over upside down on top of the boat hull, The same bagging resources could be used on both, and I sure would rather fair the peel ply than squeegeed glass cloth.
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Bill in Ottawa
I’ve been having the same debate with myself about the table build. It’s big and would use more space than I have to build. The resin infusion would require multiple resin feeds on 24’, and I sure would not risk that much set up time and material on a shop vac. Pinholes and vacuum leaks are hard enough to find, and low budget efforts at resin infusion seem like Mr. Murphy’s laws will meet Occam’s Razor with a vengeance.
My current thoughts are wet layup, peel ply and bagging the outside of the ply like a normal cold molding build - after the hull is on the strongback. I know it’ll be +10 - 20% resin heavy compared to infusion, and twice the build effort (repeating the inside glassing once done the outside, but it pushes the glassing later in the process and allows me to build the hull in sections before it gets glassed. I’ve watched Derek Kelsall’s KSS seminar DVD and gone through his material in depth, but I feel that using plywood instead of foam kind of already downgrades the result.
This kind of hull is already pretty experimental and I would rather spend the money on foam core once it is proven effective. There is no way to know if the resulting boat will be worth $2K+ of corecell, a bigger build facility etc. until you build and sail a plywood cheapie first. I also debate putting lots of money into a hull with no resale value when it is effectively a testbed. I accept the fact that people like us build proas for ourselves as everyone else just can’t get enough brain cells warmed up and functioning to bother understanding the concepts.
I also see this as building two hulls - once immersed in water and the other bigger one flipped over upside down on top of the boat hull, The same bagging resources could be used on both, and I sure would rather fair the peel ply than squeegeed glass cloth.
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Bill in Ottawa
I understand this debate down deep in my gut….
My first 3 sheet proa,P52, was way down on the cost scale, $10/sheet 5.2mm underlay ply (hence the name). The next one, Nomad, is going to be all rated ply some meranti mostly okume. Still stitch and glue, taped joints, 12 oz biaxial to just above the waterline plus some lighter stuff in the pod seating area. Most everything else id going to be painted, porch enamel over gripit. I plan on getting several years of good use out of the boat, best guess at the moment 500-700 miles a year.
Back to this thread, if it’s built, BB33, or whatever name finally appears, will be one stage up. All rated ply glass epoxy all surfaces, most of the interior precoated ultralight glass and peelply. It’s the difference in a trailer sailor and a boat that spends most of its time in the water.
I’ve never regretted the work on any boat I’ve done, but the risk goes up with boat size. Once all the questions are answered go for broke, my last canoe is kevlar and sglass over klegecell. Right now on proas I don’t even know what all the question are 😉
Cheers,
Skip
I’ve been having the same debate with myself about the table build. It’s big and would use more space than I have to build. The resin infusion would require multiple resin feeds on 24’, and I sure would not risk that much set up time and material on a shop vac. Pinholes and vacuum leaks are hard enough to find, and low budget efforts at resin infusion seem like Mr. Murphy’s laws will meet Occam’s Razor with a vengeance.
Sorry, I was being imprecise, but a quick aside first; you say your building area isn’t large enough for a table, and yet, surely the boat you build in that space will be bigger than the table?? Perhaps you mean there isn’t room for both the build AND the table? This only requires careful planning; build everything that needs the table first and set it aside, tear down the table and assemble the boat. 😉 Actually, this is fairly common with larger KSS builds.
The imprecision is where I mentioned KSS, rather than saying “pre-built on a table.” I don’t mean infusion, and I don’t mean foam, for all the reasons you so rightly point out. I mean to wet lay, bag and suck plywood to the table, all in a single step. No glass cloth on the inside of the hull—just epoxy coated and finished in peel-ply (this was used for several hundred plywood multis in the late 1970’s and 80’s, dozens of which are still extant—in the water year-round)
I wouldn’t risk a big complex infusion on a shop vac either—but I WOULD risk a single $100-in-parts sub-layup to THREE shop vacs; two of which should remain in their brand-new sealed cartons unless needed, then taken back to Home Depot when the job is done. I might borrow a generator to hold on standby for the same reason—I certainly would if I were infusing foam.
My current thoughts are wet layup, peel ply and bagging the outside of the ply like a normal cold molding build - after the hull is on the strongback. I know it’ll be +10 - 20% resin heavy compared to infusion,
In my opinion, though currently in style, it is silly to compare a bagged amateur build of a cheap non-resalable hull with infusion. Bagged and sucked is a far cry better than a simple wet layup, hand rolled and sanded back to a paintable surface. The point of bagging and sucking is to reduce labor, not increase it. 5-10# of “extra” resin left in the build just doesn’t make my event horizon, compared to either hand layup and sanding—or infusion either. 😉
I’ve watched Derek Kelsall’s KSS seminar DVD and gone through his material in depth, but I feel that using plywood instead of foam kind of already downgrades the result.
I’ve attended 2 of Derek’s workshops and I couldn’t agree with you more. Infusion is great and his methods are da bomb, but I’d only commit to it if I could start with 3-4 smaller jobs first, and *only* if the project yielded a salable boat. Plywood and construction shortcuts rather suit a design like BB33, where he wants maximum boat for the buck and looks are a ways down the list.
I also see this as building two hulls - once immersed in water and the other bigger one flipped over upside down on top of the boat hull
I like this conceptually, but I think I’d prefer to see it as a big pile of pre-cut, pre-finished sheets built as and when the spirit moves, assembled very late in the build—a sort of “instant” boat. I’m very fond of this build (though I think the boat rather ugly: http://eco5.weebly.com/kit.html
Cheers,
Dave
Thoughts on cross section:
As an asymetric boat, there is no need to have a symetrical cross section.
I would have the step only on the lee side.
To windward none, as this give least resistance to wave action, especially when heeled over.
The step can then be closer to the water, Russel’s pod has suprisingly little clearance. This then is set at bed base level, giving a bigger bed / more head room above.
(I wonder what would happen if you built an entire boat out of OSB strandboard??)
I’m a fan of OSB, it’s a cost effective material for a lot of stuff, helped my son deck a sleeping loft in granddaughters bedroom last week with the stuff. Even considered it for “marine” use above the water once.
http://www.duckworksmagazine.com/02/contest2002/06/skip.htm
But I’d be very, very leery of using the stuff below the waterline or anywhere performance really mattered.
I have that same knee-jerk response to the stuff, but let’s play devil’s advocate for a bit, can we? OSB is now rated for flooring, roofing and shear-walling in home construction—and in thinner sheets than regular plywood. So strength doesn’t seem to be a problem. Second, every little piece of wood in the matrix is coated on all sides with resin/glue. I don’t think the native wood ever gets wet, let alone rots. I may be wrong, but compare to epoxy “saturated” plywood. Virtually all the inside plies are un-coated, the manufacturer’s glue is “water proof” but not vapor-proof—the stuff gets wet everywhere there’s a nick in the hull—and that wetness can travel many feet down an unprotected ply—let alone via voids. Yes, OSB can and will get nicked too, but the intrusion is only into that single little chip of wood.
A big win, for me, is that OSB is (slightly) porous. Try sucking on it (Do this discretely, please? We proa-nuts have our reputations to consider!). Yes, plywood is porous as well, but experiments with vacuum bagging show pretty conclusively that the air will enter through and travel down the plies—not through the plywood board. Not so with OSB (I think!) This may mean you don’t need to drill all those 1/8” holes for the bagging.
Back to this thread, if it’s built, BB33, or whatever name finally appears, will be one stage up. All rated ply glass epoxy all surfaces, most of the interior precoated ultralight glass and peelply. It’s the difference in a trailer sailor and a boat that spends most of its time in the water.
You’re jumping around a little bit, Skip. I’m totally with you about horses for courses; there will be no resale, so good looks and pedigree mean little. Anti-rot and well-engineered strength mean a lot. You say “Several years at 500-700 miles/year” as the target brief. Rated ply is good for 100 yrs. Glass is great and epoxy is better, but Bacchanal (Brown Tri) is more than 40 years old and she has no glass on the inside—only epoxy. For much of BB33, I’d consider porch paint and canvas, not glass. I once re-did a deck in this stuff—the old was surprisingly well adhered. We used one-part epoxy on the new canvas, hoping for better adhesion.
I guess my point is, why not build with the minimal stack of parts which will fulfill the design brief? Fir ply, canvas or maybe just epoxy saturation—no cloth, maybe even OSB?
Thoughts on cross section:
As an asymetric boat, there is no need to have a symetrical cross section.
I would have the step only on the lee side.
To windward none, as this give least resistance to wave action, especially when heeled over.
The step can then be closer to the water, Russel’s pod has suprisingly little clearance. This then is set at bed base level, giving a bigger bed / more head room above.
I think what Michael may have been thinking (and Skip too??) is that this “T” cross section is well-known in trimarans. It is typically at counter-height, not bed height, where it has a couple of advantages—one, it gives a lot of visual space to the interior of the boat. The visual space is long and wide. Second, eliminating the windward “pod” will do what you suggest, but now you’ve substantially reduced the interior volume of the boat, actually as well as visually. Lowering the lee pod to nearer the water has no hydrodynamic advantage, and some potential disadvantage—wetted surface, wave making, negative dynamic lift. All this for a bit less total interior volume—all on one side of the boat only. The space above this bunk is hard to use efficiently—shelves? A cupboard? Just not compelling. A “T” shape offers a bunk on both sides (with or without sitting headroom, depending) and/or some really expansive counter space—for eating, cooking, navigating, puttering.
Dave
A big win, for me, is that OSB is (slightly) porous. Try sucking on it (Do this discretely, please? We proa-nuts have our reputations to consider!). Yes, plywood is porous as well, but experiments with vacuum bagging show pretty conclusively that the air will enter through and travel down the plies—not through the plywood board. Not so with OSB (I think!) This may mean you don’t need to drill all those 1/8” holes for the bagging.
Hadn’t thought of that, might be worth bagging a section of the stuff left over at son’e house to see how much epoxy soaks into the OSB. It might take quite a bit of epoxy. On the other hand all that wood really encapsulated has a lot of merit. My early exposure to OSB and “moisture resistant” MDF has left me a little leery. OTOH I’m a big fan of LVL beams.
Skip
Thoughts on cross section:
As an asymetric boat, there is no need to have a symetrical cross section.
I would have the step only on the lee side.
To windward none, as this give least resistance to wave action, especially when heeled over.
The step can then be closer to the water, Russel’s pod has suprisingly little clearance. This then is set at bed base level, giving a bigger bed / more head room above.I think what Michael may have been thinking (and Skip too??) is that this “T” cross section is well-known in trimarans. It is typically at counter-height, not bed height, where it has a couple of advantages—one, it gives a lot of visual space to the interior of the boat. The visual space is long and wide. Second, eliminating the windward “pod” will do what you suggest, but now you’ve substantially reduced the interior volume of the boat, actually as well as visually. Lowering the lee pod to nearer the water has no hydrodynamic advantage, and some potential disadvantage—wetted surface, wave making, negative dynamic lift. All this for a bit less total interior volume—all on one side of the boat only. The space above this bunk is hard to use efficiently—shelves? A cupboard? Just not compelling. A “T” shape offers a bunk on both sides (with or without sitting headroom, depending) and/or some really expansive counter space—for eating, cooking, navigating, puttering.
Dave
Yes the opening up of the interior is a big plus for the approach followed closely by the structural goodness of having some folded planes in the right places.
Skip
Mike:
I first drew up my three sheeter with a lee pod to one side and nothing to windward. Russell Brown’s designs look this way from an interior perspective, as does John Harris’ Madness. These proven designs sport a semi-enclosed “cockpit” tumor grafted on to windward, which I simplified by making the cockpit structure part of the interior design. They also add triangular soft spray deflectors from cockpit to both ends.
I live in a Northern climate where cold water is a given, and having a semi enclosed helm area is a GOOD thing. Out of the deal you get a Nav station area to one side and a galley area to the other - as well as a large bunk to leeward. Fairing this space to match the lee side just is logical and adds no major amount of material - but does perhaps make for better external aerodynamics.
I also considered making the lee pod “taller” - perhaps sitting headroom (seat to overhead 1M) - but in 24’ (@7.3M) it just is too big. I’d rather it not touch the water unless it is required for safety pod function. I personally don’t buy the whole lee pod “dynamic lift” stuff - the frequent drag of increasing wetted surface just doesn’t seem worthwhile.
I also like the spray shedding potential of the “T”‘s windward overhang. Hopefully it will suppress/redirect a lot of the normal spray at 8 knots+.
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Bill
Hadn’t thought of that, might be worth bagging a section of the stuff left over at son’e house to see how much epoxy soaks into the OSB. It might take quite a bit of epoxy. On the other hand all that wood really encapsulated has a lot of merit. My early exposure to OSB and “moisture resistant” MDF has left me a little leery. OTOH I’m a big fan of LVL beams.
If you try it, consider rolling gel coat first, then epoxy, then cloth, then slightly thickened epoxy, then OSB. No need to waste epoxy filling strandboard interstices. 😉
Dave
In response to Chris’s gentle suggestion that my preliminary Freeship model was a little uglier than need be, I went back and got things cleaned up a bit.
And it does look better! Plus I bet that the reduced stress concentrations at the transition from curved to flat, and a little added stiffness where it used to be flat, will come in handy.
Like Dave, I’m interested to see how you use the space granted by the “T”. Counter height seems perfect from an interior design point of view, but may be too low from a hydrodynamic perspective?
Very cool stuff.
chris
I first drew up my three sheeter with a lee pod to one side and nothing to windward. Russell Brown’s designs look this way from an interior perspective, as does John Harris’ Madness. These proven designs sport a semi-enclosed “cockpit” tumor grafted on to windward, which I simplified by making the cockpit structure part of the interior design. They also add triangular soft spray deflectors from cockpit to both ends.
The “T” shape hull section is certainly influenced by trimaran design, and it is also true that the spray reduction is a major benefit - you will note that even the Pacific Islanders ran spray rails along the windward gunnel of their canoes, and they were a hell of a lot tougher than I am.
But the truth is that I simply like symmetrical designs because of the savings in both material and mental thought down the road. The same panel will fit either port or starboard, fore or aft. There is a certain design elegance and flexibility inherent in the rigid symmetric. I think this comes from thinking like an Industrial Designer, in that you are never really designing for yourself, but for an imagined “other” as well. I’ll say, well, I’d like the bunk right here, but someone else might want it over there - and why shouldn’t they? So I try to come up with flexible design, that has a certain geometry behind it so that anyone can adjust as long as they keep to the general pattern.
Well, that is probably a bit much for this thread. 😉
The “T” shape hull section is certainly influenced by trimaran design, and it is also true that the spray reduction is a major benefit - you will note that even the Pacific Islanders ran spray rails along the windward gunnel of their canoes, and they were a hell of a lot tougher than I am.
But the truth is that I simply like symmetrical designs because of the savings in both material and mental thought down the road. The same panel will fit either port or starboard, fore or aft. There is a certain design elegance and flexibility inherent in the rigid symmetric. I think this comes from thinking like an Industrial Designer, in that you are never really designing for yourself, but for an imagined “other” as well. I’ll say, well, I’d like the bunk right here, but someone else might want it over there - and why shouldn’t they? So I try to come up with flexible design, that has a certain geometry behind it so that anyone can adjust as long as they keep to the general pattern.
Not sure spray reduction is much of an issue with these geometries, P52 was always dry but would bury the forward hull down to the deck coming off the top of a wave running downwind. Didn’t spend much time observing it, was really concentrated on maintaining course.
We are of similar minds about the elegance of offbeat symmetry in this little corner of the universe but my bias is towards simplicity in building and utilization. Bolgers’ Birdwatcher epitomizes this approach, I greatly admire the design on a multitude of levels. One of the things that came out of that admiration was a penchant for looking at what could be done with a parallel sided slab of plywood. P52, Nomad and BB33 all start out on the premise of wrapping the sides of a dory hull around a really fattened parabolic bottom plank (exponent = 4). BB33 carries it a little further in having the sheer follow the same sort of curve thereby opening up the interior towards the ends enough to cram a whole wish list into a four sheet solution.
At a higher D/L ratio this would be a bluff headed disaster but if we can keep the weight down enough it looks more than feasible, it looks right.
Going to a T shaped section opens up the interior dramatically and has some structural benefits. Not for counter height, tis a little too high but elbow room is to be cherished.
Skip
Skip, i’m curious, why not one single comment about the balanced rig shown?
Is it because those kinds of rigs perform too poorly that no one even considers them despite their obvious simple shunt virtue?
I guess if there was a simple, easy and high performing rig for proas, everyone would be using it.
I’m having a hard time deciding on a rig for a cruising proa.
Jzerro sloop is the default choice.
Skip, i’m curious, why not one single comment about the balanced rig shown?
Is it because those kinds of rigs perform too poorly that no one even considers them despite their obvious simple shunt virtue?
I guess if there was a simple, easy and high performing rig for proas, everyone would be using it.
I’m having a hard time deciding on a rig for a cruising proa.
Jzerro sloop is the default choice.
There’s a moderate amount of commenting on the wingsail thread and the Bionic Broomstick thread where the concept is being slowly trialed out in real life. There isn’t really that much prior art to fall back on at the moment. If I had to pick a soft sail rig today it would be a balanced club staysail as first trialed on the Broomstick. The wingsail is promising enough that it deserves some more trialing before going to a Nomad sized boat, the BB33 may well be beyond my horizon.
Cheers,
Skip